The present invention relates to a unit usable with a copier for adding extra data to those data which are printed on an original document.
While an electrophotographic apparatus or like copier is operated to copy an original document or documents, it would be very convenient from the standpoint of storage and management of copies if the date and time of copying, page numbers, manegerial numbers and other extra, as distinguished from document data printed on the documents, could be copied together with the document data. A device for adding such extra data is disclosed in, for example, Japanese Laid-Open Utility Model Publication (Kokai) 59-119442/1984 and 58-152634/1983.
In any of the prior art extra data adding devices, a display section for displaying extra data is disposed in a particular area which constitutes a part of a glass platen, or in a sliding mechanism located in the vicinity of a glass platen. This brings about a problem that the position where data can be added is either fixed or limited to a narrow range, preventing a person from adding extra data to a desired position on a copy. Another problem is that in the case that a part of the device is placed overlapping an original document which is relatively thin, the contour of the device itself appears on a copy.
While the data adding device may be implemented with a unit which is physically independent of a copier so as to allow extra data to be added in any desired position, such gives rise to another problem. Specifically, an extra data adding unit independent of a copier is incapable of interchaning signals with the copier so that, when page numbers should be added, a person has to operate a switch for changing the numerical display of the unit every time a document is replaced with another. When it is desired to number copies to facilitate management at a particular division, it is necessary to copy a single document and to provide the copies with a serial number. In such a condition, when a plurality of sets of copies are to be produced, it is impossible to continuously copy an original document by setting a desired number of copies on a copier unless the unit has a function of changing the display as instructed by a signal from the copier. Specifically, documents have to be copied one at a time while changing the display of the unit each time, consuming disproportionate time and labor.
So long as date or time is selected as extra data, no problem arises in practice. However, since the display of date and time is controlled by the clock function of the unit, the display is variable with no regard to the copier. Should the timing when the unit is rewriting the display and the timing when the copier exposes the extra data for copying it chance to coincide with each other, the transitional rewriting condition would be copied in a paper to render the extra data illegible. While such an occurrence is rare when the extra data is date, it does occur with substantial probability when the extra data is time, especially when it includes seconds. In the case that the display for extra data is implemented with an electrochromic display (ECD), it is a prerequisite that data be rewritten by deleting old data first and, then, writing new data due to its inherent characteristic. This, coupled with the slow response particular to ECD, troubles are apt to be derived from the data rewiting timing.
Another problem is that when an arrangement is so made as to allow extra data to be copied in a desired portion of a paper, difficulty is experienced in distinguishing extra data from document data in a reproduction.